7 Dec
2004
7 Dec
'04
8 p.m.
Hi all,
I remember a discussion here about slow DNS for P&T. I am experiencing
something similar with Visual Online, although I cannot say for sure if
it's their problem or mine.
This is one sample query caught by Ethereal:
Time Source Destination Protocol Info
24.107756 192.168.1.8 192.168.1.1 DNS
Standard query A www.athome.lu
29.115471 192.168.1.8 192.168.1.1 DNS
Standard query A www.athome.lu
34.125519 192.168.1.8 192.168.1.1 DNS
Standard query A www.athome.lu
39.135464 192.168.1.8 192.168.1.1 DNS
Standard query A www.athome.lu
39.165492 192.168.1.1 192.168.1.8 DNS
Standard query response A 80.92.67.138
So it means it took 15 seconds and 3 retransmissions for a DNS query to
get an answer. BTW, 192.168.1.8 is the PC, and 192.168.1.1 is the router
which forwards to VO's DNS.
This behavious is not systematic, but fairly regular (and extremely
annoying). There's 3 candidates:
-1- the PC
here's what resolv.conf says:
nameserver 192.168.1.1
-2- the router
I am unable to find anything in the logs, and I haven't changed anything
on that level except disable the RIP protocol.
-3- the DNS
not sure which one I use, as the router gets this information somehow
from VO - however, I have been unable to find any DNS specific setting
in the router. In the "LAN" tab, it says 0.0.0.0 for both the primary
and the secondary DNS server.
Any clues appreciated.
-pu
7 Dec
7 Dec
8:29 p.m.
Hi,
On Tue, Dec 07, 2004 at 09:00:14PM +0100, Patrick Useldinger wrote:
I remember a discussion here about slow DNS for
P&T. I am experiencing
something similar with Visual Online, although I cannot say for sure if
it's their problem or mine.
This is one sample query caught by Ethereal:
Time Source Destination Protocol Info
24.107756 192.168.1.8 192.168.1.1 DNS
Standard query A www.athome.lu
29.115471 192.168.1.8 192.168.1.1 DNS
Standard query A www.athome.lu
34.125519 192.168.1.8 192.168.1.1 DNS
Standard query A www.athome.lu
39.135464 192.168.1.8 192.168.1.1 DNS
Standard query A www.athome.lu
39.165492 192.168.1.1 192.168.1.8 DNS
Standard query response A 80.92.67.138
So it means it took 15 seconds and 3 retransmissions for a DNS query to
get an answer. BTW, 192.168.1.8 is the PC, and 192.168.1.1 is the router
which forwards to VO's DNS.
Is that a hardware router or a Linux box?
Those 15 seconds certainly are not normal.
I just tried here with the same request (I'm on P&T ADSL):
192.168.1.5 (my work PC):
# tcpdump -n -i eth0 udp
21:26:59.988594 IP 192.168.1.5.33178 > 192.168.1.1.53: 60911+ A?
www.athome.lu. (31)
21:27:00.030635 IP 192.168.1.1.53 > 192.168.1.5.33178: 60911 1/2/2 A
80.92.67.138 (123)
i.e. the reply was instantaneous. The resolver configured on this
machine is 192.168.1.1, which is my own router (Linux PC) with it's
own bind9. No, that host wasn't in cache, as I certainly didn't
visit www.athome.lu today (and probably not anytime in ages, if
ever).
On the external interface of the router it looks like this:
# tcpdump -n -i ppp0 udp
21:23:39.667862 213.135.230.15.1026 > 194.154.192.101.53: 42554+ [1au]
A? www.athome.lu. (42) (DF)
21:23:39.694383 194.154.192.101.53 > 213.135.230.15.1026: 42554% 1/2/3
A 80.92.67.138 (134)
So indeed my resolver went to a P&T DNS server for that query.
Again, instantaneous reply.
This behavious is not systematic, but fairly regular
(and extremely
annoying). There's 3 candidates:
-1- the PC
here's what resolv.conf says:
nameserver 192.168.1.1
Looks correct.
-2- the router
I am unable to find anything in the logs, and I haven't changed anything
on that level except disable the RIP protocol.
What kind of router? Firmware? Just in case there's anything to
be found about that particular model...
-3- the DNS
not sure which one I use, as the router gets this information somehow
from VO - however, I have been unable to find any DNS specific setting
in the router. In the "LAN" tab, it says 0.0.0.0 for both the primary
and the secondary DNS server.
Sounds like the router receives resolver information from the
dialup procedure (DHCP or whatever they use).
Any clues appreciated.
You could possibly try to manually enter DNS resolvers into the
router config? Those from VO certainly, those from P&T are also
accessible from the outside: 194.154.192.101 and 194.154.192.102
Not sure how to debug this...
Greets & hth, Eric
9:46 p.m.
Eric Dondelinger wrote:
Is that a hardware router or a Linux box?
Those 15 seconds certainly are not normal.
It is a Zyxel 650HW.
I just tried here with the same request (I'm on
P&T ADSL):
192.168.1.5 (my work PC):
i.e. the reply was instantaneous. The resolver configured on this
machine is 192.168.1.1, which is my own router (Linux PC) with it's
own bind9. No, that host wasn't in cache, as I certainly didn't
visit www.athome.lu today (and probably not anytime in ages, if
ever).
I just had a few tries, response time was 0.03-0.14 seconds. As I said,
it is not systematic, just kinda frequent.
On the external interface of the router it looks like
this:
As I have a HW router, I am unable to see what is happening there :-(
What kind of router? Firmware? Just in case
there's anything to
be found about that particular model...
ZyNOS F/W Version: V3.40(IT.4) | 11/20/2003
DSL FW Version: Alcatel, Version 4.9.10
You could possibly try to manually enter DNS resolvers
into the
router config? Those from VO certainly, those from P&T are also
accessible from the outside: 194.154.192.101 and 194.154.192.102
I also thought about caching DNS locally, with dnsmasq
(http://thekelleys.org.uk/dnsmasq/doc.html) for example. Not a solution
for seldomly used names, but at least for the frequent ones. pop.vo.lu
is a good candidate, it also sometimes takes ages to be resolved
(although Korn is looking it up every 5 minutes).
Thanks,
-pu
8 Dec
8 Dec
8:51 a.m.
Hello,
You say it is occuring only sometimes.
Could it be possible that the router is about to connect to the Internet
while your computer tries to resolve this address?
Look at connection timeout in the router config.
Another possibilty would be to configure the DNS server directly on your
computer (so it does not use the DNS relay of the router).
The DNS servers of VO should be:
80.90.44.25
80.90.45.15
Try this.
Cu,
Michel
At 22:46 07.12.2004, you wrote:
Eric Dondelinger wrote:
Is that a hardware router or a Linux box?
Those 15 seconds certainly are not normal.
It is a Zyxel 650HW.
I just tried here with the same request (I'm
on P&T ADSL):
192.168.1.5 (my work PC):
i.e. the reply was instantaneous. The resolver configured on this
machine is 192.168.1.1, which is my own router (Linux PC) with it's
own bind9. No, that host wasn't in cache, as I certainly didn't
visit www.athome.lu today (and probably not anytime in ages, if
ever).
I just had a few tries, response time was 0.03-0.14 seconds. As I said, it
is not systematic, just kinda frequent.
On the external interface of the router it looks
like this:
As I have a HW router, I am unable to see what is happening there :-(
What kind of router? Firmware? Just in case
there's anything to
be found about that particular model...
ZyNOS F/W Version: V3.40(IT.4) | 11/20/2003
DSL FW Version: Alcatel, Version 4.9.10
You could possibly try to manually enter DNS
resolvers into the
router config? Those from VO certainly, those from P&T are also
accessible from the outside: 194.154.192.101 and 194.154.192.102
I also thought about caching DNS locally, with dnsmasq
(http://thekelleys.org.uk/dnsmasq/doc.html) for example. Not a solution
for seldomly used names, but at least for the frequent ones. pop.vo.lu is
a good candidate, it also sometimes takes ages to be resolved (although
Korn is looking it up every 5 minutes).
Thanks,
-pu
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3 comments
3 participants
participants (3)
-
Eric Dondelinger -
Michel Kohl -
Patrick Useldinger